1. Field of the Invention
The present invention relates generally to devices for pumping fluids from one location to another. In particular, the present invention relates to devices and methods for obtaining groundwater samples from monitoring wells.
2. Description of the Related Art
Collection of representative groundwater samples from monitoring wells or other sampling devices has been the topic of much debate and research in the environmental field for more than twenty years. Not until the mid-1990s did the U.S. Environmental Protection Agency (“EPA”) establish a widely accepted methodology for obtaining representative groundwater samples. This accepted methodology is called the “low-flow minimal-draw down” procedure for sampling groundwater (EPA 1996). This sampling methodology was designed to have minimal impact on the water quality and chemistry of the sample collected, especially with respect to volatile organic contaminants (VOC) such as trichloroethene or benzene. Water quality and chemistry is easily altered by elevated temperatures, excessive agitation, or use of vacuum (negative pressure) to collect the samples.
Gas driven bladder pumps are commonly used for collecting groundwater samples for environmental investigations. Such pumps have a minimal effect on temperature, cause little agitation of the sample, and induce minimal negative pressure on the sampled medium.
While gas driven bladder pumps are commonly used for collecting representative groundwater samples, there are some limitations to existing systems. Two of these limitations are the amount of equipment required to conduct sample collection and the cost. To operate the gas drive bladder pump, the following equipment is typically required:
ItemEstimated Cost Range1)bladder pump$500 to $12002)pump controller$1200 to $18003)source of gas   Oiless Air Compressor$250 to $700   Compressed Gas Cylinders$10 to $20 per sample event4)Power Supply to Operate Compressor   Portable Generator  (purchase)$300 to $700            (rental)$50 to $100 per day
When sampling is conducted with the gas driven bladder pump system, a truck or van is required to contain and transport all of this equipment. One or two men may be tasked with the sampling operation. The collection of samples with this system is expensive, especially if the bladder pumps are dedicated to the wells as recommended by regulatory guidelines. There are often 5 to 10 wells at the site requiring dedicated pumps. There are literally thousands of sites around the country that require ground water monitoring on an annual basis, and many of these must be sampled every three months to meet regulatory requirements.
Because of the regulatory requirements to obtain representative groundwater samples, there is a significant need for improved methods and equipment to accomplish these goals. Gas driven bladder pumps have been the preferred equipment for collection of representative groundwater samples. Although the gas driven bladder pump provides high quality samples, it is expensive to purchase and operate, as outlined above.
Thus, there is a need in the industry for an improved device to collect representative groundwater samples at a lower cost.